Decay and preservation of building stones in non polluted enviroments (Spain)

Preservation of our Historical Cultural Heritage built in stone requires studies on the material itself, on the environment where the monument is located, and even on the microclimate affecting a particular stone in the building. Conservation treatments should be also non-agressive and restoration works should respect the chemical and mineralogical properties and surface characteristics or aesthetic aspect (colour) of the stones already existing in the monument. We have studied the intrinsic factors of several types of stones and their role in the type of degradation found in each case. Together with air pollution, salt crystallization seems to be one of the most important agents of decay, especially on porous stones and in environments where heating/cooling and wetting/drying cycles exist. Most of the results reported have been obtained on sandstones (arkosic) and granite materials used in building and restoration of monuments in Avila and Salamanca (World Cultural Heritage cities in Spain). The positive effect of several conservation and prevention treatments containing organic silicates and polysiloxane compounds, as well as methods for extracting salts by natural clays, have been studied. The results obtained represent an adequate way to evidence the problems and some of the solutions to solve them.Authors thank financial support from MCyT (grant MAT2000-0972-C02-01) and Junta de Castilla y León (CSI08/03). JGT and ACI acknowledge I3P grants from CSIC. This work is dedicated to the beloved memory of Dr. M. Angeles Vicente